| 摘要 |
A chuck includes a holder body, a clamp sleeve, and a large number of needle rollers. The holder body has a shank portion, a flange formed at one end of the shank portion, and a chuck sleeve that extends from the flange in the direction away from the shank portion. The clamp sleeve is fitted onto the outer circumference of the chuck sleeve such that the clamp sleeve is rotatable and axially movable relative to the chuck sleeve. The needle rollers are disposed between the chuck sleeve and the clamp sleeve over the entire circumference. The clamp sleeve is rotated to cause the needle rollers to revolve spirally along the outer circumferential surface of the chuck sleeve while rotating about their own axes in order to decrease and restore the diameter of the chuck sleeve. In the chuck, a groove having a predetermined depth is formed in the end surface of the flange opposite the shank portion such that the groove surrounds the base end of the chuck sleeve through which the chuck sleeve is joined with the flange. |
